1. Field of the Invention
The present invention relates to a ball screw apparatus, in particular to a ball screw apparatus in which a nut is coolable.
2. Related Art
Conventionally, in a screw apparatus including a screw shaft and a feed nut which is screwed with the screw shaft and relatively rotatable, point contact or surface contact occurs during revolutions. On this account, a cooling section is provided at a heat source (e.g., the feed nut).
As an example of the screw apparatus of this kind, there has been disclosed a screw apparatus where a cooling pipe through which coolant circulates is arranged in the feed nut as the cooling section (heat exchanger) (see e.g., Patent Document 1).
Further, as technology of cooling the feed nut, there is the invention disclosed in Patent Document 2. Specifically, this technology flows coolant in a coolant through hole (hereafter, simply referred to as a through hole) to cool down the feed nut.